The story evolves around a radio panel game show "Twenty Questions." The panel is challenged with an anonymous question. The answer leads to a series of murders in which the killer uses the programme to name his victims in advance. Two reporters spot a link between them and enlist the aid of the panel in trapping the guilty party.
Bob Beacham
Robert Beatty
Mary Game
Rona Anderson
Tom Harmon
Clifford Evans
Det. Insp. Charlton
Edward Lexy
Olive Tavy
Olga Lindo
Self - The Twenty Questions Team
Daphne Padel
Self - The Twenty Questions Team guest artiste
Jeanne De Casalis
Self - The Twenty Questions Team
Jack Train
Self - The Twenty Questions Team
Stewart MacPherson
Self - The Twenty Questions Team 'Mystery Voice'
Norman Hackforth
Self - The Twenty Questions Team
Richard Dimbleby
Maurice Emery KC
Harold Scott
Echo News editor
Liam Redmond
Mohammed Ali
Homi Bode
Gen. Maitland
Kynaston Reeves
Stewart MacPherson's secretary
Sonya O'Shea
Police Commissioner
Frederick Leister
Police Officer 'Tiny' White
Wally Patch
John Grimshaw
John Salew
Record News editor
Gordon McLeod
Cheshire Cheese waiter
Philip King
Doctor
Arthur Young
Mrs. Tavy's Neighbour (uncredited)
Merle Tottenham
Frederick 'Ricky' Tavey (uncredited)
Meadows White